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Martian Geology, Meteorites and the Perseverence Lander

Perseverance’s First Full-Color Look at Mars – Source: NASA

On February 18th, the most recent of NASA’s Martian exploration probes, Perseverence, landed on Mars after a seven month transit through space. An evolution of the design of the Curiosity rover which landed in 2012, Perseverence was designed with four objectives in mind: to identify environments that in the past could supported microbial life; looking for actual signs of that past microbial life; testing oxygen production from the martian atmosphere as a first step in considering how to prepare Mars for humans; and finally collecting rock and soil samples. In honor of NASA dropping yet another mechanical rock hound onto the surface of Mars, we’ve decided it’s time to briefly review Martian geology.

Perseverance’s Big Wheels , How This Mechanical Rockhound Gets Around – Source: NASA

What is known of the geology of the red planet comes from three sources: Martian meteorites that have ended up on earth, samples collected by rovers on the Martian surface, and remote measurements taken by orbiters, spacecraft, spacecraft etc. The first category, Martian meteorites finds on earth are rare but have been discovered. The oldest suspected Martian meteorite is ALH8400, an achondrite orthopyroxenite rock found in the Allan Hills of Antarctica in 1984 estimated to be around 4.1 billion years old (plus or minus a lot of years). Now housed in the Smithsonian, this meteorite was famously and controversially reported as having features resembling certain modern terrestrial bacteria in their appendages. According to Wikipedia “Orthopyroxenite is an ultramafic and ultrabasic rock that is almost exclusively made from the mineral orthopyroxene, the orthorhombic version of pyroxene and a type of pyroxenite. It can have up to a few percent of olivine and clinopyroxene.” ALH84001 is not only unique for its possible or possibly not connection to Martian life, it is also the only member of the Martian orthopyroxenite group of meteorites. Quite a feat.

Martian Meteorite ALH84001
Martian Meteorite ALH84001 – by Jstuby at English Wikipedia, CC BY-SA 3.0,

Besdies ALH84001, Martian meteorites are broadly classified as shergottites, nakhlites, chassignites and ungrouped. Most fall into the shergottites, named after the the meteor fall ar Sherghati, India in the mid 1800s. These are igneous rocks sub-classified as basaltic, olivine-phryic, or lherzolitic based crystal size and minteral content. In an attempt to be even more confusing this shergottites can also be classifed according to their rare earth content, and the two classification systems don’t line up with each other. Nakhlites, named after the fall in El-Nakhla, Egypt are igneous and rich augite fromed from basaltic magma on Mars from what is believed to be at least 4 separate volcanic eruptions approximately 1.5 billion years which spanned a 90 million year period. It is believed that the nakhlites in the very distant past were suffused with liquid water. The chassignites, named for the fall a Chassigny, Haute-Marne, Franceis a category consisting of two falls – the being found in the Western Sahara in 2000. Other than ALH8400, a number of other specimens fall into the other category, including the Kaidun meteorite fall from Yemen which may have originated on the Martian moon Phobos because Phobos has similarities to C-Type asteriods, and because the Kaidun is a carbonaceous chondrite which may contain fragments of material from the Martian surface. Needless to say, real martian meteorites are rare and valuable.

Slice of Martian shergottite meteor
Slice of Martian shergottite meteor – by Steve Jurvetson – Flickr: It came from Mars, CC BY 2.0,

The data retrieved from orbiters, spacecraft and other sensors in space on on the other are more complicated to explain and there aren’t any neat rock pictures to show, so we’ll move on to the rovers and their rock sampling. If turquoise, amethyst or malachite were discovered by the martian rovers it would rewrite the geology and history of Mars, not to mention spurring some of us Terrans to rush to Mars to begin setting up local rock shops to cater to the inevitable rock hounds who would start streaming there. But it’s an extremetly unlikely event. The Martian surface falls somewhere between basalt and andesite rocks of Earth. This means that some minerals formed similar to what is found on Earth. The presence of iron oxide gives the red rust color to the surface. Perchlorate in high percentages makes the soil highly saline, but also opens the possibility of extract water. Carbonate and phyllosilicate minerals formed when water was present in large amounts in the past.

The Jake Rock on Mars
The Jake Rock on Mars, an igneous rock found to be high in elements consistent with feldspar, such as sodium, aluminum and potassium, and lower concentrations of magnesium, iron and nickel than other such rocks previously found on Mars – By NASA/JPL-Caltech/MSSS – (direct link), Public Domain,

Among the phylosilicates present are kaolinite, monmoillonite, mica, and serprentine. Felsic minerals present inclute quartz, feldspar and maklynite. Gypsum, percholorate, ikaite, aragonite, ankerite, jarosite, olivine, pyroxene, augite, pigeonite, clinopyroxene, hematite, magnetite, and limenite are also present. Jarosite, incidently has been found on earth, rarely, usually as a result of mining waste exposed to rain and air, but also deep in the antarctic ice.

Adirondack - a Martian rock
Adirondack – a Martian rock, a hard, crystalline rock. The peaks large and small in Adirondack’s electromagnetic spectrum reveal that the minerals in the rock include olivine, pyroxene and magnetite – a common composition in volcanic basalt rocks on Earth – By NASA – NASA, Public Domain,

Of the mission seeking for life, well, that also has a geological slant. The rover is looking for something similar to a stromotolite, a material is formed from layerd microbial mats of photoshynthetic cyanobacteria that trap and bind sediment that can create a kind of living fossil. The belief is that if early microbial life existed on Mars, fossilized remains like stromotilite would be the most likely way to detect traces. While we wish Perseverence the best of luck in its search for life, our money is on its finding petrified wood – possibly Green Chromium Petrified Wood. That would be something. Not only would it rewrite Martian history as we know it, it might make that local Martian rock and crystal shop a profitable venture.

2.7 billion year old Tumbiana Stromatolite from an ancient lake environment on the souther margin of Pilbara Craton in Western Australia. – Source: NASA

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Welcome Stranger Gold Nugget Anniversary

This week marks the 152nd anniversary of the discovery of Welcome Stranger, the largest alluvial gold nugget ever found. Discovered 1869 in Moliagul, Victoria, Australia, the Welcome Stranger nugget had a calculated refined weight of 3,123 troy ounces and measured 2 feet by 1 foot in size.

The mid 1850s in Australia was a period of great excitement. Just as in California, gold had been discovered, and thousands traveled to Victoria looking to make their fortune. In September of 1852 gold was found in the area of Moliagul – an area which would later become famous for the discovery of Welcome Stranger.

Miners and their wives posing with the finders of the nugget, Richard Oates, John Deason and his wife. The Welcome Stranger Nugget was discovered on 5 February 1869

One of the William Parker re-enactment photos. William Parker was a photographer who had a studio in Dunolly.

Pictured are Miners & Their Wives (Including Richard Oates, John Deason & His Wife) Posing With a Replica of the Welcome Stranger Nugget

Image by William Parker –, Public Domain,

John Deason, a former tin dresser, and Richard Oates were two of the many miners who rushed to the area to make their fortune. Originally from Cornwall, England they had both staked claims in the area of Moliagul and set up small farms to support their operations. Deason was breaking the soil on his claim plot around the roots of a tree in Bulldog Gully near Moliagul in February of 1869 when he struck something hard about 3 cm below the soil. Originally thinking it was a rock, he hit it a second, then a third time. Finally clearing away the soil he discovered the massive gold nugget. Deason’s son quickly ran to the farm of Oates, his father’s partner, who was plowing his nearby paddock. Oates came over and helped cover up the nugget and they waited until dark when it would be safer to remove it. After they dug out the nugget, they held a party in order to reveal Welcome Stranger to their friends and neighbors.

Deason and Oates took the nugget into the town of Dunolly protected by a bodyguard composed of friends and sold the nugget at the London Chartered Bank of Australia for 10,000 pounds, or around $3-4 million in todays money. At that time there weren’t any scales capable of weighing this large of a nugget, so they had Dunolly based blacksmith Archibald Walls break the nugget into three pieces. The nugget was then melted down and the gold sent to Melbourne as ingots to be forwarded on to the Bank of England, leaving Australia on February 21st. The original nugget is believed to have weighed 241 lbs before being trimmed.

A story detailing the discovery was run in the Dunolly & Bet Bet Shire Express February 12th 1869, excerpted below:

The Dunolly district after having turned over a multitude of nuggets that puts every other goldfield in the Colony in the shade has at length, in the words of the Melbourne journals “beat the world” in producing the largest mass of gold on record. The ‘Welcome Stranger’ was found by two men, named John Deason and Richard Oates, on Friday last, February 5, 1869, near the Black Reef, Bull-dog Gully, Moliagul, a short distance from Wayman’s Reef, and only about a mile from the celebrated Gypsy Diggings. Deason and his mate have been working in the ground for several years past, and as is well known, had got, in digging parlance, so ‘hard up’ as to have been refused credit for a bag of flour a week or so ago, and we believe the very day before the discovery, were reminded by a tradesman that they were indebted to him for a few shillings. Still they persevered, until on the daynamed, Deason in working round the roots of a tree, at about two inches below the surface, struck something hard with a pick, and exclaimed, “D—n it, I wish it was a nugget” and had broken the pick. On stooping down to examine the obstacle, he found that the object of his dearest wish was lying at his feet, and it seemed as if the monster was so large as to be immovable. It was, however, at length released from its virgin soil, and carefully removed. The question then arose as to what was to be done with it, and the first intention was to convey it to Melbourne. When the men got to Dunolly with their prize, they were advised to take it to the bank and forthwith carried it to the London Chartered. The news of the discovery soon spread, and the bank was crowded with eager spectators, amongst whom was a number of Chinamen; and a constable was sent for to guard the prize. The weight in the gross was then found to be two hundred and ten pounds troy, and preparations were at once made to break the mass to pieces and smelt it. The appearance of the ‘Welcome Stranger’ in its pristine state was something wonderful, and it seemed impossible to realise the fact so great a mass of gold could be collected in one lump. But so it was. Many efforts were made to lift it, and many exclamations of surprise expressed at its immense weight and compactness. A sledgehammer and cold chisels were brought into requisition and several of the latter broken in the attempt to reduce into fragments the ‘Welcome Stranger’. It was found to be as solid as it looked, and as chip after chip and piece after piece was dissevered from it, its appearance was as clean as a well-cut Cheshire cheese. At length, after no less than five hours hammering, the monster was pounded up and smelted, the result being 2268 oz. 10d wts. 14 grs. of solid gold, exclusive of at least a pound weight, which was given by the delighted finders to their numerous friends, who were each anxious to retain a piece of the largest mass of gold the world has yet seen. Over nine thousand pounds were advanced on the nugget by the bank, the final value awaiting the result of assay. Some interest has been manifested as to the comparative size and value of the ‘Welcome Stranger’ and the ‘Welcome’ nugget found at Ballarat, to set which at rest we give the following particulars: -‘Welcome Nugget found in the claim of the Red Hill Company, Bakery Hill, Ballarat, on the evening of the 9th June, 1858. Weight 2,217 oz. 16d wts’. It will thus be seen that the ‘Welcome Stranger’ whose total weight (inclusive of the pieces distributed, and retained as referred to below, before being smelted) was in round numbers 2,300 ounces, being over 80 ounces heavier than the ‘Welcome’. Henceforth the almanacs, which have hitherto chronicled the Ballarat monster nugget, as the largest piece of gold on record will have to change the name to the ‘Welcome Stranger’, found in the Dunolly district, near Moliagul. Several interesting incidents might be published in connection with the finding and finders of the nugget. Oates has, we believe, neither kith nor kin with whom to share his prize, but probably soon will have. Deason has a wife and family at Moliagul, where he holds 80 acres of land under the 42nd section, which we believe he intends to settle down upon and cultivate. Oates, we understand, intends shortly to visit his home at Lands End.

Excerpt from Dunolly & Bet Bet Shire Express February 12th 1869, by gracious permission of the Dunolly Museum, Victoria, Australia

The Dunolly & Bet Bet Shire Express February 12th 1869 continued…

Since writing the above we have visited the locality to be henceforth rendered world wide in its fame. The spot where the nugget was found is marked by a post, and was pointed out to us by the two fortunate finders of this truly ‘Welcome Stranger’. Messrs. Deason and Oates inform us that they came to the colony in the year 1854. On the 19th February in that year they reached Bendigo, and from that time have been engaged as working miners, with the varied successes and difficulties appertaining to digger life. On the whole they have just managed to make a living by dint of hard work and thrift. About seven years ago they settled down at Moliagul, and have been steadily working there ever since chiefly, washing about nine inches to a foot of the surface soil in an old fashioned horse puddling machine. Mr Deason informed us that they had many times washed a whole week for half an ounce of gold, while at other times they were very fortunate. Within about a hundred yards from the spot where the ‘Welcome Stranger’ was unearthed they, some time ago, found two other nuggets, one weighing 108 ounces, and the other 36 ounces. They have stripped and washed the surface soil from several acres of land and their working are easily traced by the red clay they have bared. They informed us that this red clay contained a little gold, but not enough to pay, consequently they do not wash it. They pointed out to us a peculiar kind of red clay similar to half burnt brick, which they regard as indicative of gold, and which has always been found associated with their larger finds, and particularly so with the immense mass of gold found by them on Friday last. It is much to be regretted that this, the largest mass of gold ever found, at any rate of which there is any record, should have been melted before any model of it was made, and the fortunate owners expressed to us their regret that such had been the case. But when they discovered it the mass, as may be supposed, was unwieldy, so much so that it had to be forced from its bed by a large lever, and the place is a very solitary one, anything indeed but such a place as one would care to keep ₤10,000 worth of gold, or to risk making its discovery known until it could by surrounded by the necessary protection. The mass when found was taken to Mr Deason’s hut and placed in the fire for the purpose of rendering the quartz friable, and Deason sat up the whole of Friday night burning and reducing the mass into a somewhat manageable shape, and the debris containing it is estimated about a pound and a half weight of gold. This done, they took it to Dunolly, as previously stated, and it was at their request that the nugget was at once broken up and smelted. Some golden stone was also broken out of the Black Reef itself, specimens of, which are preserved. It is worthy of remark that at the time of our visit, Deason and his mate were working away in their shirtsleeves at the claim as if nothing had happened out of the ordinary. We are glad that the monster has fallen to the lot of such steady and industrious men.

Excerpt from Dunolly & Bet Bet Shire Express February 12th 1869, by gracious permission of the Dunolly Museum, Victoria, Australia

A wood engraving of the Welcome Stranger published in The Illustrated Australian News for Home Reader on 1 March 1869

Wood Engraving of Welcome Stranger Published March 1st, 1869 in The Illustrated Australian News for Home Reader

Image by Unknown author – [dead link], Public Domain,

There were other large nugget found in Australia, including the Holtermann Nugget discovered at Hill End, New South Wales in 1872, which weighed 290 kg. The Holtermann nugget is the single largest gold mass ever discovered, but whether it is technically a nugget remains a bit controversial. One characteristic of a nugget is that it left the lode at some point in the past and is no longer within the host rock, in other words it has broken off from the original lode of gold and has been carried away by water or erosion. The Holtermann was what was called “reef gold” after the quartz reefs often sought ought by the hard rock miners. The hand of Faith gold nugget was found in 1980 near Wedderburn, Australia and weighs in at 875 troy ounces (61 lbs, 11 oz). Other famous nuggets have been discovered in California, Alaska and Montana in the United States.

Deason returned to live in Moliagul and his descendants are still in the region,, but Oates later returned to Cornwall.

A monument consisting of a large stone obelisk surrounded by a fence was erected near the spot of the discovery of Welcome Stranger in 1897. The top image above is a replica of the nugget. A replica of the nugget is located in today in Melbourne, Victoria in the Old Treasury Building. The descendants of Deason own another replica now on display in the the town of Dunolly.

Deason and Oates Monument in Redruth, Cornwall, UK. Cornwall Gold Marketing Manager, Rachel Little; Cornwall Gold Managing Director, Dervla Jarratt; The London Mint Office. Historian, Justin Robinson; and Councillor Deborah Reeve, Mayor of Redruth. Picture courtesy of The London Mint Office. Photo reused by gracious permission of the Dunolly Museum, Victoria, Australia
Welcome Stranger 150, descendants. Picture Philip Ashton. Photo above by gracious permission of the Dunolly Museum, Victoria, Australia

Left to right (spelling to be confirmed): Harriet Caldwell; _ Mulqueen; Darcy Caldwell; Jill Caldwell; Hannah Deason; Stella Deason at rear next to Arthur Deason. Seated, Suzie Deason with Maisy Deason and Henry Deason. Black hat at rear, Jamie Deason; John Deason; Julie Deason; Pamela Deason; young bloke in red is a ‘ring in’ not related; Seated with nugget Peta Hutchinson; William Deason Ray Smith in black hat, descendant of Edward Eudy; Jim Oates; Tom Deason; Athur Deason; Lola Deason; John Deason; Kath Deason.

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Top image by photographer:Rodney Start, Museums Victoria,